igel test

This tests scheduling latency on receipt of a character on an SM501 uart.
The UART driver gets a timestamp on ISR start, and can be asked for them
from user-space after a run.
The user-space driver measures the time from ISR start to task start.
Test is specific to SH architecture.
Uses SH hardware timer.

Interbench

celleb test

Runs test with Linux on hypervisor. Hypervisor generates interrupt to Linux at periodic
intervals. The kernel measures the ISR start time, and can query the hypervisor for the
intended interrupt initiation time.

Results on page 7 are results from hdparm, normalized against a baseline configuration.
Note that page 7 shows results from a kernel with a bug (in the non-RT case).

set PPC64_TLB_BATCH_NR to 1
why?

In english translation lpar = "logical partition". This refers to a single environment under
the hypervisor. The lpar interrupt was used because it was periodic.

hdparm used for load, not for measurement. The test provided 3 different measurements of performance.

Each run is a shown as a separate path on the graph. The paths are separated to be able
to distinguish the lines. (They have different 0-bases on the graph).
point on graph shows amount of latency for each interrupt. Interrupt is on horizontal axis.

page 14 shows interrupt latency, under load.

All results are shown normalized, to avoid disclosing actual numbers for the CELL processor
and hypervisor.

Stair-step results in the graph are from hdparm being run in a loop. Sometimes hdparm was
putting load on the system, and sometimes it was not (at regular intervals).

page 15 has previous results, with non-rt kernel with bug.

page 16 shows corrected results

page 18 - load is netperf

page 26 - send performance of nonRT kernel is used as baseline for normalization.
Measurement is of network performance (with several different configurations).
Result of good performance for non-RT kernel, but with interupt threading is
not expected.

Page 28 is Owa-san's hypothesis for why the network throughput is better in the
non-rt, with irq threading, case. There are fewer hardware interrupts.
It may be because the interrupts are masked longer, so context switches are avoided. Also, because
of longer duration interrupt-off times, the network card may buffer packets, and the
network stack may be able to process more data at a time.